As a typical immiscible binary system, copper (Cu) and lithium (Li) show no alloying and chemical intermixing under normal circumstances. Here we show that, when decreasing Cu nanoparticle sizes into ultrasmall range, the nanoscale size effect can play a subtle yet critical role in mediating the chemical activity of Cu and therefore its miscibility with Li, such that the electrochemical alloying and solid-state amorphization will occur in such an immiscible system. This unusual observation was accomplished by performing in-situ studies of the electrochemical lithiation processes of individual CuO nanowires inside a transmission electron microscopy (TEM). Upon lithiation, CuO nanowires are first electrochemically reduced to form discrete ultrasmall Cu nanocrystals that, unexpectedly, can in turn undergo further electrochemical lithiation to form amorphous CuLi_x nanoalloys. Real-time TEM imaging unveils that there is a critical grain size (ca. 6 nm), below which the nanocrystalline Cu particles can be continuously lithiated and amorphized. The possibility that the observed solid-state amorphization of Cu-Li might be induced by electron beam irradiation effect can be explicitly ruled out; on the contrary, it was found that electron beam irradiation will lead to the dealloying of as-formed amorphous CuLi_x nanoalloys.

作为典型的不混溶二元系统，铜（Cu）和锂（Li）在正常情况下不显示合金化和化学混合。在这里，我们表明，当将 Cu 纳米粒子尺寸减小到超小范围时，纳米级尺寸效应可以在调节 Cu 的化学活性及其与 Li 的混溶性方面发挥微妙而关键的作用，这样电化学合金化和固态非晶化将发生在这样一个不混溶的系统中。这一不寻常的观察是通过在透射电子显微镜 (TEM) 内对单个 CuO 纳米线的电化学锂化过程进行原位研究来完成的。锂化后，CuO 纳米线首先被电化学还原以形成离散的超小 Cu 纳米晶体，出乎意料的是，_x纳米合金。实时 TEM 成像显示存在临界晶粒尺寸（约 6 nm），低于该晶粒尺寸时，纳米晶 Cu 颗粒可以连续锂化和非晶化。可以明确排除观察到的Cu-Li固态非晶化可能是由电子束辐照效应引起的可能性；相反，发现电子束辐照会导致形成的非晶CuLi _x纳米合金脱合金。